The present invention relates to a pedestrian protection device for a motor vehicle having a bumper covering and a bumper transverse support, between which a deformation element is arranged.
A known front end of a motor vehicle has, for example, a bumper transverse support, which is fastened at forward ends of longitudinal supports, and a bumper covering. A soft foam, which can be deformed at a comparatively low load level, is arranged between the bumper covering and the bumper transverse support for the protection of pedestrians. The soft foam is arranged to protect a pedestrian under certain circumstances from a direct immediate collision with a hard rigid structure, such as the bumper transverse support.
Furthermore, there is a requirement that the vehicle remain free of damage in the event of a collision in a very low speed range of, for example, up to 4 km/h, in which the pedestrian protection is not relevant because of the low speed.
In the case of a slightly higher speed, which is also not yet relevant to the pedestrian protection, there further is the requirement that damage in the event of a collision be as minor as possible and that, for example, a radiator structure situated in the front end region of the vehicle, not be damaged.
In the case of a collision at a comparatively high speed, which is no longer relevant to a pedestrian protection, there is an emphasis on the design of the motor vehicle and its crash structure to provide occupant protection. For this purpose, the vehicle front or a front end of the vehicle is designed such that it deforms in an energy-absorbing manner over a specified deforming distance.
The various requirements partly conflict with one another and require a comparatively long vehicle overhang at the vehicle front and, therefore, have a higher weight and a disadvantageous influence on the driving dynamics.
For solving the conflicting objectives arising therefrom, a bumper arrangement having a transverse support was suggested in German Patent document DE 102010054641 A1, which is fastened to the vehicle body by way of crash boxes. A pedestrian protection element for a soft impact of a pedestrian is constructed in the driving direction in front of the transverse support. In addition, a swivelable energy absorption element is provided, which can be swiveled in front of the pedestrian protection element and thereby permits an increased energy absorption in the event of collisions in which a higher collision energy absorption capacity of the crash structure of the motor vehicle is required.
German Patent document DE 102012112636 A1 also shows a bumper arrangement having a bumper transverse support and a pedestrian protection element, which can be switched by way of an actuator from a rigid state to a comparatively soft state, which serves a pedestrian protection.
German Patent documents DE 102010054641 A1 and DE 102012112636 A1 have in common that a crash or pre-crash sensor system is required, in which case, on the basis of the output signals of the sensor system, a switching-over can take place between a hard rigid state of the crash structure with a high collision energy absorption capacity and a soft state of the crash structure with a lower collision absorption capacity for the benefit of the pedestrian protection.
It is therefore an object of the present invention to create a pedestrian protection device which has a simple construction and functions independently of a sensor system and an actuator respectively.
This and other objects are achieved by a pedestrian protection device for a motor vehicle in accordance with embodiments of the invention.
A pedestrian protection device for a motor vehicle, for example, for a motor vehicle front or a motor vehicle rear, has a bumper transverse support, on whose outer side, i.e. the side oriented toward the front or to a vehicle skin (front side), a deformation element is arranged. In particular, the deformation element, i.e. particularly a deformation region of the deformation element, is arranged between a bumper covering, which forms the vehicle skin, and the bumper transverse support. The deformation element has a first element and a second element, which can be displaced relative to one another in the event of a collision. The pedestrian protection device further has a latching mechanism which, as a function of a displacement speed (and thereby of a collision speed of the motor vehicle), while utilizing a mass inertia of a latching element, which is arranged or mounted on the first element or the second element, can be adjusted between a latched state, in which a displacement of the first element relative to the second element is prevented at least partly by, in particular, a form-fitting engagement (for example, in an indentation such as a recess, or in a step), and an unlatched state, in which a displacement of the first element is permitted.
The term “bumper transverse support” can include any transverse support in the region of the motor vehicle front end or of the motor vehicle rear end.
As a result, no collision sensor system and no actuator system are required for controlling a latching of the latching mechanism. The deformation element can thereby be switched by simple means while utilizing the mass inertia, between a soft state, in which a relative displacement between the first element and the second element is permitted, and a rigid state, in which a relative displacement between the first element and the second element is prevented, as a function of the displacement speed, which is the result of the collision.
A relative displacement between the first element and the second element in this case essentially takes place in the longitudinal direction of the motor vehicle, which is usually also a main direction in the event of a frontal collision of the motor vehicle. The latching mechanism according to the present invention, independently of a collision sensor system, acts automatically by utilizing the mass inertia of the latching element.
According to a preferred further development, the latching mechanism is latched below a collision speed threshold value, and therefore a displacement speed threshold value, and is unlatched when a collision speed threshold value is reached.
The structure of the front end or of the rear end of the motor vehicle can therefore be constructed to be sufficiently rigid for a relatively low speed, so that no structural damage, for example, of the bumper covering or the like, will occur as a result of excessive deforming. Repair costs can thereby be minimized in the event of collisions at a very low speed, for example, in the case of so-called trivial damage when parking, and can be limited merely to the touching-up, for example, of paint damage.
Above the collision speed threshold value that is relevant to a pedestrian protection, the latching mechanism is unlatched, and the deformation element can be changed in its length by means of a comparatively low force for the protection of pedestrians, i.e. can be mutually pushed together by a relative displacement of the first element and the second element.
According to a preferred further development of the pedestrian protection device of the present invention, the latching element is prestressed via a spring device or can be prestressed via the spring device. For example, in the case of a displacement of the first element relative to the second element, the latching element can be engaged or latched in an indentation of the second element such that a further displacement of the first element relative to the second element is prevented.
As a result of the engagement of the latching element in the indentation, a form-locking connection takes place between the first element and the second element, so that a relative displacement between the first element and the second element will no longer be possible. In contrast, the spring device is advantageous in that an engagement of the latching element with the indentation is reliably established and maintained.
In this case, the spring device is preferably essentially relaxed in an idle state, i.e. in a state in which no collision load acts upon the deformation element.
This has the advantage that the spring device does not lose its spring tensioning force in the normal condition.
As a result, the latching mechanism preferably has a contact surface by way of which the latching element can be moved against the spring force of the spring device and can thereby be prestressed, before the latching element reaches the indentation.
In other words, the collision load is utilized for a prestressing of the spring device.
The latching element, the spring device and the indentation are preferably constructed in an interacting manner such that, in the case of a slow displacement of the first element relative to the second element, the latching element engages in the indentation and, in the case of a fast displacement of the first element relative to the second element, the latching element does not engage in the indentation.
As a result, an automatic mechanism is created which utilizes only the mass inertia of the latching element for its function. Accordingly, an engaging takes place at a low displacement speed and therefore a low collision speed, and the deformation element thus works in a rigid manner. At the fast displacement speed and therefore the fast collision speed, the latching element does not engage—in the case of the fast displacement, the latching element slides particularly over and beyond the indentation—and a further displacement between the first element and the second element is made possible, whereby the deformation element as a whole will be soft.
The spring device may additionally be equipped with a damping device, which appropriately dampens movement of the latching element. An engaging/non-engaging of the latching element can thereby be appropriately controlled.
Furthermore, according to the pedestrian protection device of the present invention, the deformation element is adapted such that, in a latched condition of the latching mechanism, it can absorb collision energy by plastic deforming and/or brittle failure of the deformation element over a predefined deformation distance. Such a deformation distance may, for example, amount to 60 mm to 110 mm.
Depending on the collision load and therefore the speed during the collision, the deformation structure can therefore react completely rigidly and transmit the collision load to the crash structure of the vehicle situated behind it, or a load threshold value of the latched deformation element is exceeded and it is deformed and can therefore absorb collision energy for the protection of other components and of the vehicle occupants.
The deformation element may have a length of from 50 to 150 mm. Preferably, the deformation element may have a length of between 70 and 110 mm.
The first element can preferably be moved relative to the second element in an unlatched state of the deformation element over a distance of, for example, 60 to 110 mm.
The first element may be a cylindrical element, which can be displaced in a corresponding guide of the second element. The latching element may be mounted on the first element or on the second element.
According to an alternative embodiment of the present invention, the first element—or the second element—may have an elastic deformable wall, which forms the spring device, particularly with a free end, wherein the free end forms the latching element.
The free end of the deformable wall can be engaged with an indentation in the second element—or in the first element.
The free end of the deformable wall can be prestressed during a displacement along a contact surface on the second element—or on the first element.
The first element—or the second element—may particularly have two opposite elastic deformable walls, which are constructed on opposite sides of the first element—or of the second element. In this case, the two walls may, in particular, be arranged symmetrically with respect to one another. The two walls may be deformable in opposite transverse directions.
The first element—or the second element—may also have three, four, or more elastically deformable walls, as described above.
Above-described further developments of the invention, to the extent possible and meaningful, can be arbitrarily combined with one another.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of one or more preferred embodiments when considered in conjunction with the accompanying drawings.